Advancements in communication technologies have permitted the introduction, and popularization, of new types of communication systems. In various of such new types of communication systems, the rate of data transmission and the corresponding amount of data permitted to be communicated, has increased relative to existing types of communication systems.
New types of radio communication systems are exemplary of communication systems that have been made possible as a result of advancements in communication technologies. Communication channels of a radio communication system are formed upon radio-links, thereby obviating the need for conventional wire-line connections between sending and receiving stations operable therein. A radio communication system, therefore, inherently permits increased communication mobility in contrast to conventional wire-line systems.
Bandwidth limitations sometimes limit the communication capacity of the communication system. That is to say, the bandwidth capacity of the communication channel, or channels, available to a communication system to communicate information between sending and receiving stations is sometimes limited. And, the limited capacity of the communication channel, or channels, limits increase of the communication capacity of the communication system. The communication capacity of the radio communication system is particularly susceptible to capacity limitation resulting from communication channel bandwidth limitations. Generally, a radio communication system is allocated a limited portion of the electromagnetic spectrum upon which to define communication channels. Communication capacity increase of a radio communication system is, therefore, sometimes limited by such allocation. Increase of the communication capacity of the radio communication system, therefore, is sometimes only possible if the efficiency by which the allocated spectrum is used is increased.
Digital communication techniques provide a manner by which the bandwidth efficiency of communications in the communication system may be increased. Because of the particular need in a radio communication system to efficiently utilize the spectrum allocated in such a system, the use of digital communication techniques is particularly advantageously implemented therein.
When digital communication techniques are used, information that is to be communicated is digitized. In one technique, the digitized information is formatted into packets, and the packets are communicated to effectuate the communication. Individual ones, or groups, of the packets of data can be communicated at discrete intervals, and, once communicated, can be concatenated together to recreate the informational content contained therein.
Because packets of data can be communicated at the discrete intervals, a communication channel need not be dedicated solely for the communication of packet data generated by one sending station for communication to one receiving station, in contrast to conventional requirements of circuit-switched communications. Instead, a single channel can be shared amongst a plurality of different sending and receiving station-pairs. Because a single channel can be utilized to effectuate communications by the plurality of pairs of communication stations, improved communication capacity is possible. Packet data communications are effectuated, for instance, in conventional LANs (local area networks). Wireless networks, operable in manners analogous to wired LANs have also been developed and are utilized to communicate packets of data over a radio link, thereby to effectuate communications between a sending station and a receiving station connected by way of the radio link.
For example, an IEEE (Institute of Electrical and Electronic Engineers) 802.11 standard defines a system for operation of a wireless LAN. The system is defined in terms of logical layer levels, and operational parameters of the various layers of the system are defined in the standard.
Proposals have been set forth to utilize an unlicensed band located at 5 GHz and to implement a WLAN operable generally pursuant to the IEEE 802.11 standard.
Other systems are also implementable at the 5 GHz frequency band. A radio communication system, referred to as the HyperLan II system is, for instance, also implemented at the 5 GHz band. The HyperLan II system is operable pursuant to a standard promulgated by the ETSI. The HyperLan II system also is a WLAN system.
As more than one communication system is operable upon common frequency portions of the 5 GHz band, communication systems operable therein must be able to dynamically select the frequency band portions upon which communications are effectuated. Dynamic selection is required so that more than one communication system does not concurrently use the same frequencies to attempt to effectuate communications.
The European Regulatory Commission (ERC) has set forth system requirements of systems operable in the 5 GHz frequency band. For instance, amongst the requirements include a requirement that a system operable at the 5 GHz band generate electromagnetic energy emissions which are spread over available frequency channels defined therein. That is, the interference level formed of the communication signal energy generated during operation of the communication system must be approximately constant over a large bandwidth of the frequency band. The interference must be spread equally and must avoid interfering with communications in satellite and radar systems.
And, for instance, an IEEE802.11 or HyperLAN system requires that a mobile station (STA) be capable of tuning to a frequency portion of the frequency band not currently used by a basic service set (BSS). And, once tuned thereto, the mobile station is required to measure for the presence of interference. Once the measurement is made, a report of the measurement must be returned to an access point (AP) of the basic service set. This procedure is referred to as dynamic frequency selection (DFS), as a result of analysis of the measurements, an access point of the basic service set determines whether to select a new frequency range for operation of the mobile station. This procedure is referred to as dynamic frequency selection (DFS). In a HyperLan II system, mobile stations report indications of a received signal strength indication (RSSI) block in a base band transceiver system as part of a DSF mechanism. Use of an RSSI indication, however, fails to provide an indication as to the source of interfering signals.
A manner better able to facilitate dynamic frequency selection in a mobile station operable in an IEEE 802.11 system would be advantageous.
It is in light of this background information related to operation of a radio communication system in which dynamic frequency allocation is utilized that the significant improvements of the present invention have evolved. 